The Pussycat Dolls star was photographed with her arm linked with the Scottish DJ in the early hours of Saturday (09Jul16), when they were spotted leaving Tape nightclub together.
The two were also snapped partying inside the hotspot, leading some to believe Calvin was using Nicole as his rebound following his recent split from another pop star, Taylor Swift.
However, an insider tells E! News there is no truth to the speculation, insisting Calvin and Nicole are strictly friends, and nothing more.
"They're casual friends, and if they see each other at a club or party they will chill," the insider says. "They are not hooking up or hanging out. Calvin isn't rebounding with anyone at this time."
While the EDM star is still single, The X Factor judge is reportedly dating tennis star Grigor Dimitrov.
And as Calvin spends time in London, British actor Tom Hiddleston has been enjoying time with Taylor in Australia. The couple, which went public with its relationship last month (Jun16), landed Down Under last week (07Jul16).
The Style star is accompanying Tom as he begins filming Thor: Ragnarok on the country's Gold Coast.
Tom even dodged questions about his romance with Taylor from a local reporter who prodded him while he was taking a breather from a jog on Saturday (09Jul16).
The newswoman asked the star, "How is Taylor enjoying the beautiful Gold Coast?", to which Tom laughed awkwardly and politely responded, "I'm not going to answer that, if it's all right."
The reporter continued to prod by asking what he and Taylor were planning to doing during their time in Australia, to which the Brit said, "I don't know... It's just good to be back."